The present invention relates to apparatus for agitating, conveying and weighing particulate material, and comprises an agitator, a scale in combination with a screw conveyor, and a drive for the agitator and screw conveyor.
Various agitators have been provided in the prior art, including agitators mounted in a generally cylindrical housing, with a pair of end wheels or end disks, and agitator bars extending between them, parallel to the axis of rotation. Typically, a shaft extended through the end wheels or end disks, being supported in bearings on the end walls of the housing. An example of such an agitator, although from a remote field, is Matthews U.S. Pat. No. 2,721,007. In order to remove the agitator for replacement, maintenance and the like, it was necessary to remove the entire shaft, and in many installations, due to adjacent structures, there was required a very cumbersome and time consuming procedure.
When weighing systems have been provided with an agitator and a screw conveyor for agitating and delivering particulate material to a weighing hopper, including a receiver and scale, the agitator and the screw conveyor were driven either by separate motors, or by an Alternating Current Motor. In such apparatus, there is a requirement that the amount of material being delivered per unit of time to the weighing hopper be adjusted, in accordance with the characteristics of the material, such as the density of it. Such weighing systems often form part of a multiple weighing system in which a plurality of particulate materials are stored and a batch is made up of a predetermined desired amount of each of the particulate materials. With such multiple component delivery systems, there is an allowable time determined for the delivery of each component to the weighing hopper, and it is desirable, as a consequence, that the screw conveyor be operated as slowly as possible so as to accurately deliver the required weight of material in the predetermined time for the delivery of that particular material. This required, as noted, adjustments of the delivery rate of the screw conveyor. In the prior art, thus adjustment was accomplished through utilization of the noted alternating current motor, and use of alternately usable sprockets, forming part of a chain drive. This provided less than optimum results, and particularly less than optimum accuracy in the delivery of material, as well as not accomplishing the intended results in the allotted time.
Among the patents in the prior art disclosing apparatus including an agitator and a conveyor are MOORE et al. U.S. Pat. No. 2,633,272, FARLEY U.S. Pat. No. 2,650,002, and MEYER U.S. Pat. No. 3,310,205.
In the known particulate material handling systems in which particulate material is stored, delivered to a conveyor, and from the conveyor to a weighing hopper, it is known to provide a delivery conduit which extends downwardly to the receiver of the weighing hopper, and to provide a valve in the delivery conduit. As the particulate material passes through the delivery conduit and reaches the receiver, the total weight of the particulate material in the receiver increases, and the weight of the material in the receiver is constantly weighed. When the scale indicates that the desired total weight is being approached, the valve in the delivery conduit is closed; this may be done either manually or automatically. In either case, the delivery conduit valve is closed prior to the weight in the receiver of the weighing hopper reaching the final desired total weight, since it is known that there is particulate material in flight in the delivery conduit. Another factor which must be considered is the time allotted for the delivery of the desired amount of particulate material, with consequent increase or decrease in the speed of operation of the screw conveyor, and consequently there is a different amount of material in flight, depending upon the speed of operation of the screw conveyor. The greater the speed of the screw conveyor, set to deliver the required amount of material in a relatively short time, causes an increase in the amount of material in flight during any given time span. Consequently, the point at which the cut-off valve is caused to be closed depends upon the rate of delivery of the material, so that for a higher rate of delivery of material, deriving from a higher speed of the screw conveyor, the noted valve is caused to be closed when the receiver of the weighing hopper has a relative lesser amount of particulate material in it, than would be the case where the speed of the screw auger is relatively slower, and there is, as a consequence, less material in flight during the same time span.
Heretofore, the desired accuracy of the weighed amount of particulate material has not always been achievable, due in part to an assumption which has not proven to be valid. That assumption is that the particulate material in flight is of uniform consistency, and is therefore of uniform specific weight. That is, it is assumed that every increment of particulate material reaching the receiver has the same volume and weight as every other increment. In fact, it is now been found that this assumption is not always valid, leading to errors in the amount of particulate material weighed.
Screw conveyors have long been used for conveying a wide variety of materials. Some materials which are now being conveyed in screw conveyors are particulate, being finely divided, and some of the material tends to remain in the screw conveyor. Thus, when the particular storing, delivering and weighing system is utilized for a different particulate material, contamination may occur. The prior art screw conveyors, particularly when associated with agitators, have not been constructed so as to permit ready cleaning thereof.